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MORPHOLOGY OF THE KNIPOVICH RIDGE AREA
OS31A-0972
Yulia Zarayskaya, Sergey Sokolov, Anastasia Abramova, Ksenia Dobrolyubova, Alexander Mazarovich and Eugene Moroz
Russian Academy of Sciences, Laboratory of Ocean Floor Geomorphology and Tectonics, Geological Institute, Moscow, Russia
Abstract
Knipovich Ridge is the northernmost part of the Mid-Atlantic Ridge system. It is located between Mohns and Molloy spreading centers in the Greenland Sea.
The scientific team of the R/V “Akademik Nikolaj Strakhov” (Geological Institute RAS, Russia) surveyed this area in 2006, 2007, 2009 and 2010
using the deep-water multibeam echosounder RESON Seabat 7150 with working frequency 12 kHz.
The total surveyed area is up to 82000 km² including 65000 km² covering rift valley and flanges of the ridge.
Knipovich ridge is classified as an ultraslow oblique spreading center with spreading rate around 1,4 cm/y.
Its large-scale morphological features are reduced in number comparing to other mid-ocean ridges.
Eastern flange is buried under the continental slope sediments and only the rare highest peaks rise above this cover.
Western flange is fully developed and consists of several ridges prolonged parallel to the rift valley.
Ridges are supplemented with individual highs. Rift valley is 20-40 km wide and 500 km long. Its depth is 3300-3700 m.
Valley slopes have terraces and ledges of different amplitudes. The bottom of the valley is echeloned by 5 volcanic axial highs rising 400 - 1000 m above it.
S24-P1-06
Spreading obliquity is imprinted in the ridge morphology. The global models predict a plate motion vector of 307°.
The main ridge axis has general orientation of 350°. Rift valley follows this direction from the South, and on the half way to the North turns to azimuth of 2°.
The detailed bathymetry shows that small-scale features orientation differs from that of the large-scale.
Rift axial highs and individual flange highs are prolonged NW-SE under azimuth 30°. This orientation is sub-perpendicular to the plate motion vector (83°) and
oblique to the ridge axes (40°). The multibeam bathymetry shows no sing of transform faults or non-transform discontinuities along the Knipovich ridge rift valley.
There is one strong lineation in the northern part of the ridge. It includes flange and axial highs and continues from the eastern flange
through the second northern axial high to the western flange under the azimuth of 320°.
It is an indication of long-term magmatic activity in this segment.
Bathymetric map of the Knipovich Ridge
magmatic segment
The detailed bathymetry shows multiple
volcanic structures of central types.
Elevation of volcanic structures above the bottom
of the rift valley is 500 m.
Detailed bathymetry reveals small-scale features that are important for the understanding of the ridge nature.
Ultraslow spreading class of ocean ridges
Survey Area
R/V “Akademik Nikolaj Strakhov”
Spreading rate < 20 mm/year
Shaded-relief multibeam bathymetric map of
the northern part of the Knipovich rift valley
illuminated from the northwest. Contour interval is 100 m.
The detailed bathymetry shows the small-scale features.
General rift valley azimuth is 2°.
Rift axial highs and faults are prolonged NW-SE under azimuth 30°
oblique to the ridge axes (28°)
CHIRP profile S24-P1-06 fragment.
The profile shows thrust faults on the northern part
of the Knipovich ridge west flange.
Ultraslow spreading ridges (red lines): G - Gakkel Ridge, Kn - Knipovich Ridge,
M - Mohns Ridge, K - Kolbeinsey Ridge, R - Reykjanes Ridge, RS - Red Sea Rift,
AB - Aden Ridge, AAR - American-Antarctic Ridge, SWIR - Southwest Indian Ridge.
Bathymetry - GEBCO, 2008.
CHIRP profile S25-P5-08 fragment.
Orientation of the main structures in
The profile shows normal faults on the southern part shear zones of different types
of the Knipovich ridge east flange.
(Kirmasov, 2011).
Arctic bottom topography map.
Bathymetry - IBCAO 2.23 (Jakobsson, M., et al., 2008)
Grey polygon shows R/V “Akademik Nikolaj Strakhov”
(Geological Institute RAS, Russia)
survey area in cruises of 2006, 2007, 2009 and 2010.
Total surveyed area is up to 82000 km².
Methods
Conclusion
Deep water multibeam echosounder
RESON SeaBat 8150 (7150)
• frequency - 12 kHz
• 234 receiver beams across swath
• 2°x2° beams
• swath coverage 150°
• distance between tracks – 4 - 7 km
• horisontal datum - WGS84
• vertical datum - mean sea level
• data acquisition and processing onboard
in PDS2000
Result - digital terrain model (100х100 m)
Schematic diagram of the modern tectonics
of the North Atlantic and Arctic divergent structures
(Sokolov et al., 2014).
Multibeam echosounder working station
onboard R/V “Akademik Nikolaj Strakhov”.
Installation of multibeam echosounder gondola
on R/V “Akademik Nikolaj Strakhov”.
Detailed bathymetric map of the Knipovich Ridge. Contour interval is 100 m.
Lines show the location of the CHIRP profiles.
Acknowlegements
Work was conducted under the joint program of Geological Institute of Russian Academy of Science and Norwegian Petroleum Directorate
“Late Mesozoic - Cenozoic Tectono-Magmatic History of the Barents Sea Shelf and Slope as a Clue to Paleodynamic Reconstructions in the Arctic Seas”
as a part of the International Polar Year.
I would like to thank all people from the Laboratory of Ocean Floor Geomorphology and Tectonics at GIN RAS and the crew of the R/V “Akademik Nikolaj Strakhov”.
I thank Nippon Foundation GEBCO training program at the Center for Coastal and Ocean Mapping at UNH and AGU Student Travel Grant program for there support
and opportunity to present the work at AGU Fall Meeting 2014.
GEBCO Science Day at AGU Fall Meeting 2014
Shaded-relief multibeam bathymetric map of
the southern part of the Knipovich rift valley
illuminated from the northwest. Contour interval is 100 m.
General rift valley azimuth is 350°.
Rift axial highs and faults azimuth is 30° as in the northern part.
Obliquity to the ridge axes is 40°.
The Knipovich ridge is the key structure for understanding
tectonic and geodynamic nature of the transition zone
between the North Atlantic and Arctic spreading centers.
Detailed bathymetry depictured small-scale features
such as faults, hills and volcanic structures within the rift valley
and on ridge flanges. Morphology of the structures
shows incoherent orientation of the small-scale feature and
the rift axis. Orientation and distribution of the normal
and thrust faults as well as general orientation of the
system of the spreading and transform centers between
Mohns and Gakkel ridges suggests that the plate boundary
develops within the big transtensional shear zone.
Thrust faults and normal faults distribution scheme for Northern
part of the Knipovich Ridge between 77°20’ N and 78°40’N
according to the interpretation of the disjunctive dislocations of the
upper sediment layer in high-frequency seismic profiles
(Sokolov et al., 2014).
References
Contacts:
Jakobsson, M., R. Macnab, L. Mayer, R. Anderson, M. Edwards, J. Hatzky, H. W. Schenke, and P. Johnson, 2008,
An improved bathymetric portrayal of the Arctic Ocean: Implications for ocean modeling and geological, geophysical
and oceanographic analyses, Geophys. Res. Let., 35: pp. 1-5, doi: 10.1029/2008GL033520.
Kirmasov A.B. 2011, Fundamentals of structural analysis. Scientific World, 368 pp.
Sokolov S. Yu., Abramova A.S., Zarayskaya Yu.A., Mazarovich A.O., Dobrolyubova K.O. 2014, Modern tectonics of the
northern part of the Knipovich Ridge, Atlantic. Geotect., 3: pp. 16-29, doi: 10.7868/S0016853X14030060
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